1. Field of the Invention
The invention relates to compositions of vault complexes containing cytokines, such as the chemokine CCL-21, and use of vault complexes for delivering the cytokines to a cell. The vault complexes include a fusion protein of the cytokine of interest fused to major vault interaction domain. Also included in the invention is the use of the compositions as cancer immunotherapy agents for activating an immune response against a tumor and for treating cancers, including lung cancer.
2. Description of the Related Art
Vaults are cytoplasmic ubiquitous ribonucleoprotein particles first described in 1986 that are found in all eukaryotic cells [1]. Native vaults are 12.9±1 MDa ovoid spheres with overall dimensions of approximately 40 nm in width and 70 nm in length [2,3], present in nearly all-eukaryotic organisms with between 104 and 107 particles per cell [4]. Despite their cellular abundance, vault function remains elusive although they have been linked to many cellular processes, including the innate immune response, multidrug resistance in cancer cells, multifaceted signaling pathways, and intracellular transport [5].
Vaults are highly stable structures in vitro, and a number of studies indicate that the particles are non-immunogenic [6]. Vaults can be engineered and expressed using a baculovirus expression system and heterologous proteins can be encapsulated inside of these recombinant particles using a protein-targeting domain termed INT for vault INTeraction. Several heterologous proteins have been fused to the INT domain (e.g. fluorescent and enzymatic proteins) and these fusion proteins are expressed in the recombinant vaults and retain their native characteristics, thus conferring new properties onto these vaults [7,8].
CCL-21 has been identified as a lymphoid chemokine that is predominantly and constitutively expressed by high endothelial venules in lymph nodes and Peyer's patches and by lymphatic vessels, stromal cells in the spleen and appendix [9]. CCL-21 binds to the chemokine receptor CCR7 and is a chemoattractant for mature DCs, naive and memory T cells [10,11]. This chemokine, along with CCL-19, is required for normal lymphoid tissue organization that is ultimately essential for effective T cell-DC interactions. Natural killer (NK) and natural killer T (NKT) antitumor effectors express the CCR7 receptor and are chemo attracted by CCL-21. The use of chemokines that attract DC, lymphocyte, and NK and NKT effectors into tumors can serve as an effective antitumor strategy. Based on this concept, it has been previously shown that intratumoral administration of recombinant CCL-21 reduces tumor burden in murine lung cancer models [12]. The antitumor responses induced by recombinant CCL-21 however required high and frequent dosing because proteins administered intratumorally are not retained locally for prolonged periods. Although these studies delineated the role of CCL-21 as an effective antitumor agent, frequent high dose intratumoral administration is clinically limiting with the potential of unnecessary systemic toxicity. Based on the limitations of this approach, the use of autologous dendritic cells for intratumoral CCL-21 delivery was examined [13.14]. In preclinical studies, it was demonstrated that intratumoral administration of CCL-21 gene modified dendritic cells led to tumor eradication in murine lung cancer models. Following this initial description of the antitumor properties of CCL-21, several other research groups have reported that CCL-21 has potent antitumor properties in a variety of model systems [15-19]. In all models, CCL-21 demonstrated potent regression of tumors, which was shown to be dependent on host T cell immunity. Based on extensive pre-clinical evaluation, the intratumoral injection of DC transduced with an adenoviral vector expressing the secondary lymphoid chemokine gene (Ad-CCL-21-DC) was assessed in a phase I trial in advanced non-small cell lung cancer (NSCLC).
While clinical studies utilizing intratumoral administration of chemokine gene modified DC show promise as an effective therapy, the preparation of CCL-21 expressing autologous dendritic cells is cumbersome, expensive and time consuming. A reagent that is efficacious and works through a similar therapeutic mechanism is highly desired. Compositions and methods are needed to circumvent autologous DC preparation, minimize batch to batch variability and allow for comparability and standardization. There is a need for cytokine delivery, e.g., a non-DC based approach for intratumoral CCL-21 delivery for the purpose of initiating antitumor immune responses
Vaults are generally described in U.S. Pat. No. 7,482,319, filed on Mar. 10, 2004; U.S. application Ser. No. 12/252,200, filed on Oct. 15, 2008; International Application No. PCT/US2004/007434, filed on Mar. 10, 2004; U.S. Provisional Application No. 60/453,800, filed on Mar. 20, 2003; U.S. Pat. No. 6,156,879, filed on Jun. 3, 1998; U.S. Pat. No. 6,555,347, filed on Jun. 28, 2000; U.S. Pat. No. 6,110,740, filed on Mar. 26, 1999; International Application No. PCT/US1999/06683, filed on Mar. 26, 1999; U.S. Provisional App. No. 60/079,634, filed on Mar. 27, 1998; and International Application No. PCT/US1998/011348, filed on Jun. 3, 1998. Vault compositions for immunization against chlamydia genital infection are described in U.S. application Ser. No. 12/467,255, filed on May 15, 2009. The entire contents of these applications are incorporated by reference in their entirety for all purposes.